Broaching is an excellent method of machining many materials when both precision and high production rates are required. In particular, it is widely used in the automotive industry for forming various contours into engine blocks. While the rate of production of broaches is high, this has been somewhat offset in the past by the relatively high costs of the initial broach and of resharpening the broach after it has become dulled. To overcome the latter of these difficulties, various designs using indexable and reversible inserts have been introduced. However, not all of these designs have been capable of producing cuts that were as precise or economical as could be desired. In particular, some of these designs resulted in uneven chip load upon the inserts which is thought to cause precision lessening vibration. In addition, uneven chip load also results in inserts wearing at varying rates so that either all inserts are indexed at one time even if only some are worn or when production is stopped for indexing or replacement, the worn inserts are indexed or replaced but production is again halted later when other inserts become worn. Either procedure is less than ideal.
A further detriment to some of these designs is found in the uneven power requirements resulting from rows of inserts entering the workpiece simultaneously. Thus, with those designs presenting rows of inserts, the power required would increase suddenly each time a row of inserts contacted the workpiece then decrease suddenly each time a row left the workpiece. It is thought that in some cases, this might have contributed to vibration and hence harmed precision.
The cutter assembly of the present invention provides a broach whereby the chip load on the various inserts can be made more uniform and the power requirement fluctuations caused by multiple inserts simultaneously entering or leaving the workpiece can be reduced.